In the manufacture of disposable pens for thermal ink jet printing systems, it has been one practice to employ metal electroplating processes to form the outer ink ejection orifice plate of the pen to a desired contoured geometry. This orifice plate is also sometimes referred to as a nozzle plate, and will typically be adhesively secured to and precisely aligned with an underlying thin film resistor (TFR) substrate. In this structure, a plurality of resistive heater elements will normally be aligned with an associated plurality of ink reservoirs from which ink is ejected through orifice openings in the covering orifice plate during an ink jet printing operation. This type of thin film resistor printhead structure is described, for example, in the Hewlett-Packard Journal, Vol. 36, No. 5, May 1985, incorporated herein by reference.
In addition to the above HP Journal disclosure, other types of nickel orifice plates and related electroforming processes are described in U.S. Pat. No. 4,694,308 issued to C. S. Chan et al. entitled "Barrier Layer and Orifice Plate for Thermal Ink Jet Printhead Assembly", and in copending application Ser. No. 915,290 of C. S. Chan et al. entitled "Improved Barrier Layer and Orifice Plate for Thermal Ink Jet Printhead Assembly and Method of Manufacture", filed Oct. 3, 1986 now U.S. Pat. No. 4,716,423. Both the patent and the copending application are assigned to the present assignee and are incorporated herein by reference. In addition to the above disclosures, a related electroforming process for manufacturing a compound bore nickel orifice plate for an ink jet printhead is disclosed and claimed in U.S. Pat. No. 4,675,083 issued to James G. Bearss et al. on June 23, 1987, also assigned to the present assignee and incorporated herein by reference.
The metal orifice plates disclosed in the above identified references have proven highly acceptable in terms of improving ink ejection efficiency and performance and in reducing ink cavitation wear and ink corrosion, thus increasing the printhead lifetime. However, these metal orifice plates are opaque and thus do not enable one to actually view the fluid dynamics which occur beneath the orifice plate and above the associated thin film resistor substrate during an ink jet printhead testing and evaluation operation.